The present disclosure relates to an image forming apparatus and a developing unit.
An image forming apparatus based on electrophotography includes a photoconductor drum on which a toner image is formed, and a developing unit for supplying the toner to the photoconductor drum. The developing unit includes a developing roller disposed close to and parallel to the photoconductor drum.
The developing unit is removably installed in the main body of the image forming apparatus. However, since the developing roller is located close to the photoconductor drum as stated above, the developing roller may contact the photoconductor drum in a mounting or removing process of the developing unit.
Accordingly, some image forming apparatuses are configured to move the developing roller away from the photoconductor drum before the developing unit is removed from the main body (technique A).
According to the technique A, the developing unit includes a housing, a developing roller and a magnetic roller disposed parallel to each other, and a bearing unit rotatably supporting the respective end portions of the developing roller and the magnetic roller.
The bearing unit is disposed to swing about the axial center of the magnetic roller, together with the developing roller. The bearing unit is biased by a first spring, so that the developing roller is abutted against the photoconductor drum. An arm member is provided in the vicinity of the magnetic roller of the bearing unit.
The housing includes a shaft member movably extending in the axial direction of the magnetic roller. The shaft member is biased by a second spring so that an end portion sticks out from the housing. The shaft member reciprocally moves in contact with the arm member, so as to cause the arm member and the bearing unit to swing about the axial center of the magnetic roller.
The main body includes a holder unit on which the developing unit is mounted, and an openable cover unit located forward of the holder unit.
Upon closing the cover unit with the developing unit mounted on the holder unit, the end portion of the shaft member which has been sticking out is abutted against the rear face of the cover unit and made to retreat against the biasing force of the second spring. At this point, the arm member and the bearing unit are made to swing by the movement of the shaft member, and the developing roller is pressed and abutted against the photoconductor drum by the biasing force of the first spring.
Conversely, upon opening the cover unit the shaft member is allowed to stick out forward by the biasing force of the second spring. Because of such movement of the shaft member, the arm member and the bearing unit are made to swing against the biasing force of the first spring, and therefore the developing roller moves away from the photoconductor drum.